This bike will go as far as you are willing to ride it. There are a few on here who have made some really long trips. If you remember to stop and do the maintenance it will keep on going.

I ride about 18 miles one way to work part of which is on I-270 around St. Louis. Like most major cities, this is the circular interstate which loops around town. The traffic will slow to a crawl one moment and turn into a mini Nascar race the next. I've had my S40 for one summer and just passed 2500 miles riding like this and have never been in a spot yet where I needed quicker  pickup. Have gone on a couple 100 mile rides and other than the seat, it is acceptable. No one's going to mistake it for a Goldwing however.

I started on a Rebel myself. The Savage/s40 is IMO the best step up bike from the 250 cruisers. Its almost as light, almost as cheap, easier to maintain than most except the gz250 which its basically equal to in maint. and has a GREAT deal more kick. It also have a few quirks. look up "plug leak" and "cam chain tensioner" on the search function. My '95 will do 70 without even trying and will definately hit the indicated 100mph. I havent gone more than a few hundred miles at a time but Ive had no issues with it keeping up on the interstate. You'll stop before the bike as long as you keep it maintained. On long rides check your oil level frequently.

The S-40 would be a good choice. I use mine mostly in city as a commuter and some hwy cruising on weekends. This bike likes them both equally IMO. Just today i had to run the interstate for about 40 miles and the bike and i loved it. There was a moment where i needed to get out of a hole i was in and a twist of the throttle took me from 65 to 80 in a matter of seconds. This bike has great response and it's quick!!!!

MichaelK wrote on 09/08/08 at 19:03:58:
The only limitation I can think of is if by "sustained high speed" you mean in excess of 80 mph.

I have a 2000 that I obtained in '04 with just over 5K on the clock.  It had the stock muffler, I replaced with a nice very loud Harley Fishtail, and then with a slightly quieter MAC on the insistance of Wife1.0.  The cover over the idle screw was missing, I do not know if the PO did anything else to the carb, but the bike runs fine.  It is about to turn 25K and I have yet to even look at the spark plug.  It merges onto the freeway (60-65mph) easily in third gear, I timed the 40-70 mph roll-on at 6 to 8 seconds, it'll do an indicated 80 no problem, but 85 on our pavement starts rattling my eyeballs.  This bike is a LOT quicker and faster than I'll ever need.

Last September was a GEEIA Reunion in OKC, I took the bike.  L.A. to O.K.C. was via the superslab.

Gardena-Barstow, 127 miles, 135 minutes, 56 mph (L.A. traffic.)  Gas and food and lookythar stops sure eat into travel time, but managed to do the 570 miles to Holbrook AZ that first day, mostly 65-70 mph pacing traffic.  Day two was 520 miles into Amarillo TX, again running about 70 mph, but needing more and more rest stops.  60 year old body just can't take the sitting in one position endlessly.  But the Bike did jes' fine.

Lots of gas stations along the Interstates, you can use http://www.truckstopinfoplus.com/ to plan out stops at <=140 miles using 24-hour truck stops/ so the smallish tank is not a trip killer.

I have a new saddle, and I want to add floorboards for the next Reunion, about a year from now, in Fort Worth -- should ease the pain of long hours in the saddle.

The return to L.A. was via US-60 / CA-62 at a more reasonable 55-60 and roughly 300 miles/day.  MUCH more enjoyable.  While the superslab traffic is 50-100 cars per mile, the old roads are more like 5 miles per car.  Need to know your gas stops better, but if you simply gas up on your hourly butt breaks it's still not a problem.

3 hour interstate trip to NYC with no problems.  Mostly in the rain, nonetheless.  Go for it!  

First, thanks to all for the input.  I'm leaning more and more towards trading the GZ in for the s40 by midwinter or so.

mornhm:  In fact no, I wouldn't use the S40 for much superslab riding at all.  It would be mainly an around town(St. Cloud, MN) and commuter bike to work and back(20 miles, round trip), where speeds wouldn't and legally can't exceed 55mph on county highways.

I'm just playing with the idea of riding the bike down to a family reunion in Illinois next July....I'm now pretty convinced  that it would indeed be possible....Thanks again for the advice everyone.